1. Field of the Invention
The present invention relates to fasteners for flexible sheets or films.
2. Prior Art
U.S. Pat. Nos. 3,987,835 and 3,805,873 illustrate typical edge fasteners for flexible sheets utilizing a rigid channel, and an insert bar that fits over or is secured to the flexible sheet and then is held in the channel.
These devices work satisfactorily in many applications, but in some places it is desired to have a very secure lock on the film even though the use of a lock entails additional costs and takes some additional space.
Insert members for the channels such as those shown in the above identified patents have been modified to provide a resilient force tending to lock the insert member against portions of the channel. Such a device is shown in U.S. patent application Ser. No. 100,549, filed Dec. 5, 1979. The devices of this type are sold by Park Fastener Company, Colorado Springs, Colo. In those devices the insert which goes into the retainer channel for holding the polyethylene or other sheet film in place includes means to resilently urge one edge of the insert against a detent surface of the channel to pinch the sheet between the insert and the surface of the channel to provide a secure holding force.
Additionally, a structure such as that shown in U.S. Pat. No. 3,893,212 and 3,999,258 has been used for holding a sheet of material. These devices include a flexible support channel as well as a lock insert. The channel and insert cooperate to pinch a sheet of material to hold it along its longitudinal length.
In some instances support channels have utilized edge retainer clips that clip over the upper edge of one wall of the channel and hold a layer of film placed over the edge of that channel. Such a device is shown in the advertisements of The Nexus Corporation, for their "S.C. Lok System". Further, it has been known to insert a flexible tube between upright walls of a channel insert similar to that shown in FIG. 14 of U.S. Pat. No. 3,987,835 so that the opposite walls of the insert are forced against the legs of the channel to pinch the sheet being held and securely lock it in position.